Dogweed and Deathcap was a shop in Hogsmeade that sold exotic plants and flowers[1], presumably including the Death-Cap.

Etymology

"Dogweeds" are daisy-like flowers in Thymophylla genus which are known to grow in regions of the U.S. and Mexico. "Deathcaps" are a poisonous fungus that can be lethal if ingested and is widespread across Europe. Interestingly, neither of these are actually known to be useful or have any particular lore about them (besides the fact that deatcap is toxic).